Using the Ka, pH, and pKa to Predict the Relative Strengths of Weak Acids:

 

 

 

1.    Which is the larger number:     4.8 X 10-6   or    1.2 X 10-1 ?

 

2.    Consider an acid solution with a Ka value of  1.2 X 10-2.  Is this acid classified as a weak acid or a strong acid?  Why?

 

 

 

 

 

 

3.    As the percent of ionization increases, the strength of the acid _______________.

 

 

4.    You are given two weak acids:  for Acid A, Ka = 1.2 X 10-2;

       for Acid B, Ka = 1.8 X 10-5.

 

        Which of these acids is stronger?

 

5.    As the Ka value increases, the acid strength ___________________.

 

       As the Ka value decreases, the acid strength ___________________.

 

6.    Look again at Question 4 above. What is the pKa value for each of these acids?

 

Answer:        For Acid A, the Ka is 1.2 X 10-2.  Its pKa is _________________.

                    For Acid B, the Ka is 1.8 X 10-5.  Its pKa is _________________.

 

 

7.    As the pKa value increases, the strength of the acid  ___________________.

As the pKa value decreases, the strength of the acid ___________________.

 

8.    If you have a low pH value, is the acid weak or strong?

 

 

 

 

 

 

 

 

 

 

 

ANSWERS:

 

  

Using the Ka, pH, and pKa to Predict the Relative Strengths of Weak Acids:

 

 

 

1.    Which is the larger number:     4.8 X 10-6   or    1.2 X 10-1 ?

 

9.    Consider an acid solution with a Ka value of  1.2 X 10-2.  Is this acid classified as a weak acid or a strong acid?  Why?

 

Answer:  It is a weak acid.  Why?  -Because it has a Ka value.  That means that the ionization products of this acid are in equilibrium with its molecular form.  It is not highly ionized, and it is not a strong acid.

 

10.  As the percent of ionization increases, the strength of the acid increases.

 

 

11.  You are given two weak acids:  for Acid A, Ka = 1.2 X 10-2;

       for Acid B, Ka = 1.8 X 10-5.

 

      Which of these acids is stronger? Acid A is stronger because its Ka value is higher.

 

12.  As the Ka value increases, the acid strength  increases.

As the Ka value decreases, the acid strength decreases.

 

13.  Look again at Question 4 above. What is the pKa value for each of these acids?

 

Answer:        For Acid A, the Ka is 1.2 X 10-2.  Its pKa is 1.9.

                    For Acid B, the Ka is 1.8 X 10-5.  Its pKa is 4.7.

 

 

14.  As the pKa value increases, the strength of the acid  decreases.

As the pKa value decreases, the strength of the acid  increases.

 

15.  If you have a low pH value, is the acid weak or strong? strong.